Method and apparatus for correlating a pipeline inspection record to known external locations

ABSTRACT

Apparatus and methods are disclosed for correlating a pipeline inspection record to known external locations along the pipeline. Inspection signals produced by inspection apparatus transported through a pipeline are recorded on magnetic tape along with regularly occurring coded time signals produced by a time code generator. At known locations external to the pipeline the passage of the inspection apparatus through the pipeline is detected and the exact time of passage is recorded either at the respective known locations, or via telemetry, at a base station. Magnetic tape having inspection signals and time coded signals is correlated with time signals recorded when inspection apparatus passed known locations to indicate the position of known external locations on the inspection record.

United States Patent 1 91 Carter et al.

[ Aug. 21, 1973 LOCATIONS lnventors: Nick G. Carter; Charles C. Moore,

III, both of Houston, Tex.

Assignee: AMF Incorporated, White Plains,

Filed: Sept. 17, 1971 Appl. No.: 181,406

[56] References Cited UNITED STATES PATENTS 2,601,248 6/1952 Brenholdt.324/67 MAR/(ER 35 574 mm 57:4 770 x'm 34 110.2 I

MARKER lvo.

INSPECT ION EQUIPMENT 7/1960 Gregory 346/59 12/1964 Hall 346/33 PPrimary Examiner-Joseph W. Hartary iittorri ey-Geo rge W. Price and IohnGallagher [5 7] ABSTRACT Apparatus and methods are disclosed forcorrelating a pipeline inspection record to known external locationsalong the pipeline. Inspection signals produced by inspection apparatustransported through a pipeline are recorded on magnetic tape along withregularly occurring coded time signals produced by a time codegenerator. At known locations external to the pipeline the passage ofthe inspection apparatus through the pipeline is detected and the exacttime of passage is recorded either at the respective known locations, orvia telemetry, at a base station. Magnetic tape having inspectionsignals and time coded signals is correlated with time signals recordedwhen inspection apparatus passed known locations to indicate theposition of known external locations on the inspection record.

17 Claims, 5 Drawing Figures BASE 574 770A! .STR/P CHART RECORDER 66SIGNALS DR/ VER DRIVER 0N IDE/VT/F/CA T/ON CORRELATUR 75 SHEET 2 BF 3DIGITAL PATENTED M1821 1973 MAG. TAPE PLAYBACK (S/G/VAZ BASE 5m r/o/vMAG. TA PE PLAYBACK BY CHARLES C. MOORE,HI

ATTORNEY J INSPECT/0N SIGNALS 556.

m mm T EM VC mG K K N Y H L A m m M L 0 0 F. N N 6W A n A k M C I 2 0987654 0 0555555 3 22 2 3 fizv aflwudfi M MHMMMMMA lll lul lI-l-llllllHOUR MIN.

DAY-

BACKGROUND OF THE INVENTION Buried pipelines are inspected to detectanomalies in the wall of the pipe by passing an instrumented devicecalled a pig through the pipeline. The pig is propelled through thepipeline by the fluid product being transported therethrough andnondestructive testing apparatus carried by the pig continuouslyinspects the condition of the pipe. Electrical inspection signalsproduced by the testing apparatus are continuously recorded on amagnetic tape recorder, for example, which is carried by the pig. Afterthe instrumented pig has completed its inspection run through a sectionof the pipeline, the tape record is recovered and played back onappropriate apparatus to produce a visual record of the inspectionsignals. An operator then views and interprets the visual record todetermine the condition of the pipe.

After viewing the inspection record it may be concluded that one or morelocations along the pipeline should be excavated in order to inspect thepipe in further detail and/or to replace one or more lengths of pipe.Because an inspection run of the instrumented pig may traverse fromfifty up to or exceeding one hundred miles of the buried pipeline, theinspection record necessarily is made on a greatly reduced linear scalewith the consequence that accurate determination of distance andcorrelation of the record to known external locations are difficult.

Considerable trouble and expense are involved in ex cavating any pointalong the pipeline. Consequently, to avoid excavating at the wronglocations, it is extremely important that the recorded inspectionsignals be accurately correlated to actual distance along the pipelineand to known external locations along the pipeline. In the past it hasbeen difiicult to achieve the desired accuracy in this correlation. Theinspection apparatus usually produces a discernable signal each timetheapparatuspasses a girth weld in the pipeline. The lengths of sections ofpipe between girth welds may be obtained from construction records ofthe pipeline, and by counting the number of girth welds on a record, anestimate of actual distance on the record may be made. However, ininterpreting a complete record which may represent from 50 up to 100miles of pipeline, it is easy for an operator to error in counting themany signals which correspond to girth welds.

SUMMARY In accordance with one embodiment of the invention, aninstrumented pipeline pig carrying nondestructive testing apparatus, atime code generator, and a magnetic tape recorder is passed through asection of buried pipeline. At external locations spaced along the routeof the pipeline at intervals of approximately a mile, means are providedfor detecting the passage of the pig past the respective locations.Means also are provided at each external location to transmit a uniquelocation identification signal to a base station at the instant the pigis detected.

The base station includes means for receiving the transmissions from theknown locations and for recording the location identifying signals alongwith coded time signals from a time code generator located at the basestation. The base station time code generator has a known timerelationship to the time code generator carried by the pipeline pig. Thetime coded signals recorded at the base station are correlated with thetime signals on the record made in the pig and an inspection record isproduced having thereon the inspection signals and time signals recordedin the pig, and indicia which identifies on the record the knownexternal locations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified illustration ofapparatus for making two magnetic tape recordings; one having inspection signals and coded time signals recorded thereon, and the otherhaving time coded signals and marker station signals which indicate whenthe inspection pig passed a respective marker station;

FIG. 2 is a simplified block diagram illustrating means for correlatingtime signals on two magnetic tapes to identify on a strip chart read outof inspection signals the locations of marker stations;

FIG. 3 is a representation of a short section of a strip chart made bythe apparatus of FIG. 2; and

FIGS. 4 and 5 are simplified illustrations of means for practicing analternative embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS In FIG. 1, a pipeline 10 is buriedperhaps three or four feet below the surface of the ground 11. FIG. 1 isintended to represent several miles along a pipeline. For simplicity ofillustration and discussion, only several segments have beenillustrated. An instrumented pipeline pig 12 is illustrated at aparticular location within the pipeline. The pig includes elastomericpackers l4 and 15 which are in sliding contact with the wall of thepipeline. The fluid product being transported through the pipeline urgesagainst packers I4 and 15 to propel the pig through the line.

Pig 12 contains inspection equipment 18 for conducting nondestructivetesting or" inspection of the pipeline as the pig is propelledtherethrough. Inspection equipment 18 may include one or more of manyknown types, such as magnetic, eddy current, acoustic, ultrasonic, orradiological. Whatever type of inspection is performed, it is assumedthat the equipment produces inspection signals on one or more outputleads 20. The inspection signals contain information relative to thecondition of the pipe.

As illustrated in simplified form in FIG. I, pig 12 is instrumented toperform magnetic flux leakage type of inspection. A source of magneticflux 21 establishes a flux field in the wall of pipeline l0. Flux source21 may be a solenoid which is energized by batteries carried by pig 12.A plurality of flux leakage detector means 22 are carried by the pig andare in sliding contact about the wall of the pipe to detect leakage fluxcaused by anomalies in the pipe wall. Anomaly signals from detectormeans 22 are appropriately processed by the inspection equipment 18 andappear in analog form on output leads 20. The inspection signals may beconverted to digital form by equipment carried by pig 12 -if it is sodesired.

Pig 12 also carries recording apparatus such as mag netic tape recorder24 which has the capability of recording many input signals onrespective tracks on the magnetic tape.

A time code generator (TCG) 26 also is carried in pig 12 and its codedoutput signals which occur at regular intervals of I second, forexample, are recorded on one or more appropriate tracks on tape recorder24. Many types of time code generators are known and may be used in thepractice of this invention. In general, time code generator 26 includesan accurate digital clock and means to provide a time code output in agiven format. Although FIG. 1 illustrates one output lead from time codegenerator 26, it is to be understood that there may be a number ofparallel output leads which correspond to the number of bits in theparticular code format employed. There are a multitude of codes andformats known in the art, and any may be employed. One example of asuitable time code generator is Model 8150 produced by Systron-DonnerCorp., Concord, Calif. This generator is capable of being synchronizedwith a known time standard such as the time transmissions from the radiostations of the U.S. National Bureau of Standards. At least two outputsare provided by this time code generator. One is a standard IRIG B BCDtime code format, and the other is a standard BCD digital clock output.

In accordance withthis invention, marker stations are temporarilyestablished at spaced intervals of perhaps each mile along the route ofthe section of pipeline to be inspected. Each marker station iscomprised of a sensor means 30 which is capable of detecting thepresence of pig 12 as it passes the marker station. Sensor means 30 maybe housed within a tube or stake which is driven into the groundimmediately above pipeline 10. As illustrated in FIG. 1, sensor 30 is areed type proximity switch which normally is in the open condition. Inthe presence of magnetic flux lines that extend parallel to the reedcontacts of the switch, the reed contacts are forced into contactingrelationship to close the switch. A suitable reed type proximity switchis described in U.S. Pat. No. 3,544,934. In the embodiment of theinvention illustration in FIG. I, the magnetic field established bysolenoid 21 on pig 12 will extend outwardly beyond pipeline l and willbe sensed by the reed switch. Other sensing arrangements may beemployed. For example, pig 12 may carry means for radiatingelectromagnetic, acoustic, ultrasonic, or radiological energy and sensormeans 30 will be a suitable detector which actuates a relay or othercircuitry when it senses the radiation from the pig.

Sensor 30 is connected to a modulator circuit 32 and activates thatcircuit when pig 12 is detected. Modulator 32 producesa modulatingsignal which keys a radio transmitter 34 associated with each markerstation. The signal from transmitter 34 is radiated by antenna 35 towarda base station 40 which will be described below. Because it is desiredto know when pig passes each of the marker stations, it is preferablethat the modulator 32 associated with each marker station gen erate acoded signal unique to that station.

Base station 40 includes antenna 41 and radio receiver 42 which receivesignals transmitted from the respective marker stations. One output leadfrom receiver 42 is coupled to a timer circuit 45 which is triggered bya suitable signal from the receiver 42 to provide timing signals for theoperation of base station 40. A received marker station signal, which isuniquely coded in digital form to identify the sending marker station,is coupled to a serial to parallel converter 46 and then stored instorage register 47.

A synchronized time code generator 50 has its parallel output leadscoupled to normally closed gate 51 whose operation is under control of afirst output signal from timer 45. Time code generator 50 may be thesame type of apparatus as employed for TCG 26 in pig 12. The coded timesignal which is in time code generator 50 at the instant a markerstation signal is received at base station 40 is gated through gate 51by a gating signal from timer 45 and is stored in storage register 54.The respective coded signals in registers 47 and 54 then aresimultaneously shifted out of the registers by a shift pulse coupledfrom timer 45 on lead 56. The shifted coded signals both are recorded onmagnetic tape recorder 58 in a manner so that they may be read outsimultaneously. A signal from timer 45 then is coupled over lead 59 totape advance means 60 to step advance the magnetic tape of recorder 58so that it is in condition to record another received coded markerstation signal and a simultaneously occurring coded time signal when atransmission is received from the next marker station along thepipeline.

It should be understood that the simplified representation of basestation 40 in FIG. 1 is only an example since other apparatus and otherinstrumentations may be utilized to accomplish the desired result. Thecoded signals may be processed and recorded partially or wholly inserial fashion rather than parallel as illustrated. Any of the manyknown types of codes and code fonnats may be used for the time codedsignals and for the coded marker station signals. Additionally, manytelemetry systems and apparatus are known and may be used in thecommunication link between the marker stations and the base station.

Prior to the time that pig [2 is launched into pipeline 10, a knownfrequency and time relationship is established between the time codedgenerators 26 and 50. This may be accomplished by synchronizing bothgenerators to a known standard. In accomplishing this synchronization, amodel 890A VLF/LF Receiver, manufactured by Tracor IndustrialInstruments, Austin, Texas may be used. This device can be used tocompare the frequencies of the oscillators in the time code generators26 and 50 with a reference frequency. An accurate frequency reference isprovided by radio transmissions from the U.S. National Bureau ofStandards radio station WWVB. A known relationship is also establishedbetween the time indications provided by the two time code generators.This may be done by synchronizing both generators to the time signalstransmitted by NBS radio station WWV. As a matter of convenience, timecode generators 26 and 50 provide time signals based on real time. Othertime bases may be used.

After pig 12 has completed an inspection run through a section ofpipeline 10 the pig is recovered and the magnetic tape is obtained fromrecorder 24. 1

In order to accurately correlate the records of the inspection signalson the tape from the pig recorder 24 to the known external locations ofthe marker stations, it is necessary to correlate the recorded timesignals on the two tapes. This may be accomplished with the use ofapparatus illustrated in simplified form in FIG. 2. Magnetic tapeplayback devices 62 and 64 are provided to play back the respectivemagnetic tapes from piglZ and base station 40 of FIG. I. Playback device62 provides inspection signals on a plurality of output leads 66. Thesesignals, assumed to be in analog form,

are coupled to input terminals of strip chart recorder 67 which producesa visual recording of the inspection signals. A number of differenttypes of strip chart recorders are known. One suitable type is a lightbeam oscillograph recorder designated Model 1508 Visicorder,manufactured by Honeywell, Test Instrument Division, Denver, Colo.

Playback device 62 also provides on output leads 69 the continuouslyoccurring coded time signals that were recorded in pig 12. These codedtime signals are coupled over leads 70 to an alpha-numeric driver, orconverter, 71 which contains a numeric character generator that providesappropriate signals to permit strip chart recorder 67 to write the timesignals on the strip chart in numbers representing the day, hour,minute, and second, for example, corresponding to the coded time signal.A suitable device for alpha-numeric driver 71 is a Honeywell Model 1204Visiprinter. The strip chart recorder records time in a manner toprovide an accurate real time scale for the inspection signals.

The coded time signals on leads 69 also are coupled as one set of inputsto digital correlator 75. The other set of inputs to the correlator arecoded time signals on leads 76 from the base station playback device64.. Playback device 64 operates in step fashion, the tape beingadvanced in incremental steps by a step signal on an input lead 77. itwill be recalled that at each incremental position of the tape inplayback device 64 there is recorded a coded marker station signal and acoded time signal which represents the time that the pig was detected atthat station.

in operation, digital correlator 75 holds a base station coded timesignal from playback device 64 and compares this time signal against thecontinuouslychanging pig time signals from playback device 62. When acomparison, or correlation, of two time signals occurs, an output pulseis produced on lead 79. This pulse is coupled over lead 77 to playbackdevice 64 to step it to its next incremental position at which the nextcoded marker station signal and accompanying coded time signal isrecorded.

The correlation signal on lead 79 also is coupled to gate 81 whoseinputs are the coded marker station signal which identify the markerstation associated with the correlated time signal. Gate 81 is opened bythe correlation signal on lead 79 and passes the coded marker stationsignal to alpha-numeric driver 84 which may be identical to the driver71. The output signals from alpha-numeric driver 84 are coupled to stripchart recorder 67 which then produces on the strip chart a visualnumeric record or indicium which uniquely identitles the correspondingmarker station. The marker station indicia on the strip chart arelocated to precisely identify the known location of the marker stationwith reference to the inspection signal records and the recorded numerictime signals.

An example of how a short strip of the printed record from strip chart67 might appear is. illustrated in FIG. 3. The analog inspection signalsappear on the right side of the strip and the numeric print out of timesignals appears along the left side. At the extreme left edge of thestrip a station marker indicium is printed out to show the time that thepig passed that known external location along the pipeline. Looking nowat the recorded inspection signals is seen that the girth welds in thepipeline were detected by all of the detector means on the pig and thatanomalies in the pipe were detected by some but not all of the detectormeans. By knowing exactly where the marker stations are located, and bycounting girth'weld indications from the nearest marker station, and byknowing the approximate speed of travel of the pig in the pipeline,which can be obtained from the information on the strip chart, theactual locations of detected anomalies in the pipeline may be determinedwithcorisiderable accuracy.

As previously mentioned, inspection signals may be recorded in digitalform in pig 12. They also may be read out in the tape recorder 67, FIG.2, in digital form.

it may be desired to prepare a master magnetic tape having thereon allof the correlated information that is contained on a strip chart readoutfrom recorder 67, FIG. 2. This may be easily done by recording all ofthe input information in digital form. Referring to FIG. 2 and assumingthat recorder 67 is a magnetic tape recorder, the inspection signals onleads 66 will be converted to digital form if they are not in that form.The respective time signals on leads 69 and 82 already are in digitalcoded form so that they may be recorded on the master tape in that formby eliminating alpha numeric drivers 71 and 84. if conversion to anydifferent codes or code formats is desired before recording'on a mastertape, known conversion apparatus is commerciaily available or can beconstructed by those skilled in the art.

it will be appreciated that means other thanan exclusive radio link maybe used to transmit time and marker station identification informationback to a base station. For example, the marker stations and basestation may be tied into existing private or commercial communication ortelemetry systems.

Because of geographical considerations and/or because of powerlimitations on the radio transmitting equipment, it may be necessary touse two or more base stations disposed at spaced locations along .thesection of pipeline to be inspected. if a plurality of base stations areused, all will have their time code generators syn-. chronized with astandard time source, and each one will receive transmissions from anassigned number of marker stations along a given portion of the pipelineroute. On playback to correlate the time signals recorded at the basestations with the time signals re-' corded in the pig, the magnetictapes from the base stations will be successively played back in theirproper order and correlated with the pig magnetic tape.

FIG. 4 illustrates means for practicing the present invention whereintime information for accurately locating the marker stations is nottransmitted to a base station but is made available at the respectivemarker stations.

In FIG. 4, the instrumented pig 12 is identical to the one illustratedin FIG. 1 and functions as described to provide in tape recorder 24 amagnetic tape having re corded tracks of inspection signals and anaccompanying record of the coded time signals from time code generator26.

Marker stations No. l and No. 2 include a pig sensor means 30 fordetecting the presence of the pig 12 at the respective marker stations.Each marker station includes a timepiece 87 which may be synchronized toa known standard and which may be turned off in response to a signalfrom a pig detector circuit 88 which functions to produce the desiredsignal when sensor, 30 senses the presence of pig l2. Timepieces 87 maybe a digital clock, a time code generator, or any type of chronometerwhich may be stopped or which will provide a time readout in response toa suitable signal.

In operation, time code generator 26 in pig 12 is synchronized with, ora know time relationship is established with, the timepieces 87 at eachof the marker stations. With the marker stations in operation, pig 12passes through pipeline l performing its inspection function duringwhich it records on a magnetic tape in recorder 24 inspection signalsand time coded signals. When pig 12 is sensed at marker station 1,timepiece 87 is stopped, or provides a time readout, to indicate theexact time the pig was sensed at that station. As pig 12 continues itsrun through the pipeline, marker stations located successively furtheralong the pipeline will provide respective indications of the time thatpig 12 was sensed. After pig 12 has completed its inspection run of asection of the pipeline it will be recovered and the magnetic taperecord will be obtained.

The method for correlating the known locations of the marker stations tothe inspection records and time record made in the pig will be describedby referring to FIG. 5. Playback device 90 plays back the recordedmagnetic tape from pig l2 and the inspection signals, which are assumedto be analog, are coupled over leads 92 to strip chart recorder 94 wherethey are recorded as visible traces as in FIG. 2. Coded time signalsfrom playback device 90 are coupled out on output lead 95 as codedelectrical signals. These signals may be in parallel form or in seriesform as indicated in FIG. by the single output lead 95. If it isdesirable that the coded pig time signals be recorded on recorder 94 inreal time numeric figures, appropriate apparatus such as code readerand/or converter 97 and character generator 98 will be provided.Character generator 98 may be the same type of apparatus as describedfor alpha numeric driver 84 in FIG. 2.

It may be acceptable to record the coded pig time signals on the stripchart of recorder 94 in a coded form, either symbolic or numeric, ratherthan converting them to numeric real time. With a little practice, anoperator may read and interpret the recorded coded signals withconsiderable speed and facility.

The marker stations are visited by one or more crew members of theoperating team to obtain the times that are registered on each of thetimepieces 87. Having obtained this information an operator scans thestrip chart of recorder 87 to find the corresponding times on the stripchart. He then enters appropriate marker station indicia oridentifications adjacent the appropriate recorded times on the chart.

The present invention also may be practiced in the inspection ofpipelines that are under water, such as the pipelines that connectoff-shore platforms with shore facilities. In such an environment themarker stations also would be under water'and in a system operatingsimilarly to that shown in FIG. 1, their transmitters would transmitsonic energy to a sonar-type receiver which may be located near theshore or near the offshore platform. Alternatively, the marker stationmay utilize a radio transmitter and antenna carried by a buoy that ismoored to or adjacent the submerged pipeline. As a further alternative,the marker stations and base station may be connected by a cable.

In the explanations given above in connection with FIG. I it was assumedthat a marker station transmitted a signal to base station 40 at theinstant that pig 12 was detected, and it was further assumed that thismarker 8 station signal, and a corresponding time code signal from TCG50 was recorded on magnetic tape recorder 58 at substantially the sameinstant. In some telemetry systems known in the art there is a measuredtime delay between the occurrence of a detected event and theidentification of the transmitted signal at a base station. This delayoccurs because of the manner of signal processing at the base station.This type of telemetering system often is employed when there is alimitation on the power of the radio transmitter at the telemeteringsending station. In efiect, what is accomplished in such a system is atrade-off of transmitter power against transmission time. In theprocessing of the received information at the receiving station, theequipment recognizes the signal that indicates the occurrence of anevent at the sending station and automatically produces a correct timeread out from information contained in the received transmission fromthe sending station. Such a system may be utilized in the practice ofthe present invention and is intended to be included in the scope of thefollowing claims. v

We claim:

l. A method for making a pipeline inspection record having thereonindications of known locations along the pipeline, said methodcomprisingthe steps performing nondestructive inspection of the pipelinewith apparatus that moves through the pipeline and past'said knownlocations,

making on the apparatus a record of nondestructive inspection signals asthe apparatus moves through the pipeline,

simultaneously with the performance of the nondestructive inspection,providing on said record of inspection signals a time scale to representtime during the recording of said inspection signals,

sensing externally of the pipeline to detect the arrival of theinspection apparatus at known locations spaced along the route of thepipeline,

operating externally located timing means to provide respective timeindications which represent the times the inspection apparatus isexternally sensed at the known locations,

searching a record of said inspection signals and time scale to identifypositions on saidrecord where the recorded time correspond to saidexternally produced time indications.

2. A method for producing on pipeline inspection record indications ofthe times that a pipeline pig passed respective known external locationsspaced along the pipeline, said method comprising the steps moving apipeline pig through the pipeline and past said known externallocations, making with apparatus including timing and recording meanscarried by the pipeline pig a continuous record representing incrementsof time that occur during movement of the pipeline pigthrough thepipeline,

producing with means including timing means loeated externally of thepipeline time indications representing the times that the pipeline pigpassed the respective known locations,

removing said continuous record from said pipeline pig at the conclusionof its passage through a given length of the pipeline,

identifying those time increments that were recorded in the pig whichcorrespond to the respective time indications that were producedexternally when the pipeline pig passed the respective known locations.

3. The method claimed in claim 2 and including the following step whichis performed prior to passing the pig through the pipeline,

establishing a known time relationship between the timing means carriedby the pipeline pig and the timing means located externally of thepipeline.

4. The method claimed in claim 2 where the step of externally producingtime indications includes,

sensing the passage of the pipeline pig past said known locations by theuse of externally located sensing means that produces respectivedetection signals, and

producing said time indications in response to said detection signals.

5. A method for indentifying on a pipeline inspection record therelative position of a known location along the pipeline, said methodcomprising the steps performing an inspection of the pipeline withapparatus that moves through the pipeline and past said known location,

making on the apparatus a first record of inspection signals as theapparatus moves through the pipeline, simultaneously with theperformance of the inspection, providing on said record of inspectionsignals successively occurring indications of time, detecting thepresence of said apparatus at a known location along the pipeline, andexternal to the pipeline, providing a detection signal upon detection ofthe apparatus, a

providing in response to said detection signal, and

with means that includes a timepiece located external to the pipeline, arepresentation of the time the moving apparatus was detected at saidknown location,

comparing a record having said inspection signals and said successivelyoccurring time indications thereon with said representation of the timethat the inspection apparatus arrived at said known location to identifythe time indication on the record which corresponds to the time that theapparatus arrived at the known location.

6. The method claimed in claim 5 and further including the stepsproducing in response to the detection signal a coded signal identifyingsaid known location, transmitting the coded signal to a base stationlocated remotely from the known location,

receiving the transmitted coded signal at the base station, producing atthe base station successively occurring time signals that bear a knowntime relationship to the indications of time recorded on the firstrecord,

recording on a second record at the base station the time signalproduced there which represents the time the coded signal was receivedfrom the known location, and

comparing the first and second records to identify the time indicationon the first record which corresponds to the time signal on the secondrecord.

7. A method for making a pipeline inspection record having thereonindications of known external locations along the route of the pipeline,said method comprising the steps placing one of a plurality oftimepieces in a pipeline pig and placing the remainder of saidtimepiecesexternal to the pipeline to be inspected,

establishing a known time relationship between said timepieces,

moving the pipeline pig containing said one timepiece through thepipeline,

performing nondestructive inspection of the pipeline with apparatuscarried by the pig as it moves through the pipeline and past said knownexternal locations,

making in the pig a continuous record of nondestructive inspectionsignals as the pig moves through the pipeline, simultaneously with therecording of inspection signals, recording on said record successivelyoccurring representations of time as determined by said one timepiece,

sensing externally of the pipeline to detect the arrival of the pig atthe respective known locations,

producing respective indications of time as determined by the externallylocated remainder of the timepieces in response to said sensing of thepig at the known locations,

removing said record from the pipeline pig,

searching said record of inspection signals and successively occurringtime representations, or a re cord corresponding thereto, to identifythe positions on the record where the time representations correspond tosaid-indications of time.

8. The method claimed in claim 7 wherein the step of producingrespective indications of time in response to said sensing of the pig atthe known locations includes the steps 35 transmitting a respectivesignal from each known location in response to the sensing of the pigthereat,

receiving said transmitted signals at a base station located remotelyfrom said known locations, said re mainder of the timepieces beinglocated at said base station,

successively recording at the base station respective time indicationsprovided by said remainder of the timepieces in response to saidsuccessively received signals.

9. The method claimed in claim 8 and including the steps playing backthe record produced in said pig and the record produced at said basestation and producing playback inspection signals and respectiveplayback time signals of recorded times on said records,

correlating the playback time signals,

producing a correlating signal when the playback time signals are incorrelation,

simultaneously with the playing back of said two records, producing athird record of the playback inspection signals, and

producing an indicia on said third record in response to saidcorrelating signal to indicate adjacent the inspection signals therelative positions of the known locations.

10. Apparatus for making a pipeline inspection record and for indicatingon the record the relative position of a known location along the routeof the pipeline, comprising the combination inspection apparatus forproviding inspection signals representing detected pipeline conditions,

means for moving the inspection apparatus through the pipeline,

timing means moving with the inspection apparatus through the pipelinefor providing time signals,

means included with said inspection apparatus for simultaneouslyrecording said inspection signals and said time signals,

means external to the pipeline for providing a second time signalindicating the time the moving apparatus arrived at said known location,

playback means for playing back the record of inspection signals andtime signals and for making an inspection record of said inspectionsignals,

correlating means operating simultaneously with said playback means forcorrelating playback time signals with a signal corresponding to saidsecond time signal for producing an indicium signal when correlation isachieved, and

means for entering an indicium on said inspection record whencorrelation is achieved in the correlating means.

11. Apparatus claimed in claim and further including means forestablishing a known time relationship between said timing means and themeans external to the pipeline,

said known time relationship being established prior to inserting thepipeline inspection apparatus within the pipeline.

12. Apparatus for making a pipeline inspection record and for indicatingon the record the relative position of a known location along the routeof the pipeline, comprising the combination inspection apparatus forproviding inspection signals representing detected pipeline conditions,

means for moving the inspection apparatus through the pipeline,

timing means moving with the inspection apparatus through the pipelinefor providing time signals,

means included with said inspection apparatus for simultaneouslyrecording said inspection signals and said time signals,

means including a second timing means external to the pipeline forproviding a record of the time the moving apparatus arrived at saidknown location, said second timing means having a known timerelationship to the timing means moving with the inspection apparatus,

means for comparing said two records to identify the time signal on therecord made on the inspection apparatus which corresponds to therecorded time that the device arrived at said known location.

13. Apparatus for making a pipeline inspection record and for indicatingon the record the relative positions of known locations along the routeof the pipeline, comprising the combination inspection apparatus forproducing inspection signals representing detected pipeline conditions,

means for moving the inspection apparatus through the pipeline and pastsaid known locations,

a first timing means included with said apparatus for producing timesignals as the apparatus moves through the pipeline,

means included with said apparatus for simultaneously recording saidinspection signals and said time signals as the apparatus moves throughthe pipeline,

means located externally of the pipeline at each of said known locationsfor detecting the'presence of said apparatus at each of the respectivelocations and for producing respective detection signals upon detectionof said apparatus at each of said locations, additional timing meanslocated externally of the pipeline, the additional timing means having apredetermined time relationship with the first timing means, meansexternal to the pipeline and operably connected with said additionaltiming means for producing a respective time indication in responsetoeach of said detection signals, and means for comparing the recordedtime signals on the record made in the pipeline with the respective timeindications produced externally of the pipeline to identify the timesignals which were recorded when the apparatus was detected at therespective known locations. 14. The apparatus claimed in claim 13 wherethe additional timing means located externally of the pipeline includesa plurality of timepieces each located at a respective known location,and wherein said means operably connected to the additional timing meansincludes respective means at each known location responsive to a'respective detection signal for causing the respective timepiece toproduce a time indication.

15. The apparatus claimed in claim 13 wherein the means external to thepipeline and operably connected to said additional timing meansincludes,

transmitting means located at each of said locations and responsive to arespective detection signal for transmitting a corresponding detectionsignal to a base station located remotely from the known locations,

receiving means located at said base station for receiving saidcorresponding detection signals from the known locations,

said additional timing means comprising a second timing means at saidbase station, means responsive to said received corresponding detectionsignals and operable with said second timing means for producing asecond record of successive time indications produced by the secondtiming means at the times that respective corresponding detectionsignals were received. 16. The apparatus claimed in claim 15 and furtherincluding playback means for simultaneously playing back the recordproduced in the pipeline and the second record produced at the basestation, thereby to produce corresponding playback inspection signals,playback time signals, and playback time indications,

means for correlating said playback time signals and said playback timeindications to produce a correlation signal each time a predeterminedcorrelation is achieved,

means for producing a third record of playback inspection signals, and

means responsive to correlation signals for providing an indicium onsaid third record to identify the in spection signals that occur incoincidence with a 3,754,275 13 14 correlation signal, thereby to locateon said third means responsive to said playback time signals for :F therelative wsltions ofsaid knmvn loca recording corresponding times onsaid third record ions. 17. The apparatus claimed in claim 16 andfurther including along with the recorded inspection signals.

5 i t i i

1. A method for making a pipeline inspection record having thereonindications of known locations along the pipeline, said methodcomprising the steps performing nondestructive inspection of thepipeline with apparatus that moves through the pipeline and past saidknown locations, making on the apparatus a record of nondestructiveinspection signals as the apparatus moves through the pipeline,simultaneously with the performance of the non-destructive inspection,providing on said record of inspection signals a time scale to representtime during the recording of said inspection signals, sensing externallyof the pipeline to detect the arrival of the inspection apparatus atknown locations spaced along the route of the pipeline, operatingexternally located timing means to provide respective time indicationswhich represent the times the inspection apparatus is externally sensedat the known locations, searching a record of said inspection signalsand time scale to identify positions on said record where the recordedtime correspond to said externally produced time indications.
 2. Amethod for producing on pipeline inspection record indications of thetimes that a piPeline pig passed respective known external locationsspaced along the pipeline, said method comprising the steps moving apipeline pig through the pipeline and past said known externallocations, making with apparatus including timing and recording meanscarried by the pipeline pig a continuous record representing incrementsof time that occur during movement of the pipeline pig through thepipeline, producing with means including timing means located externallyof the pipeline time indications representing the times that thepipeline pig passed the respective known locations, removing saidcontinuous record from said pipeline pig at the conclusion of itspassage through a given length of the pipeline, identifying those timeincrements that were recorded in the pig which correspond to therespective time indications that were produced externally when thepipeline pig passed the respective known locations.
 3. The methodclaimed in claim 2 and including the following step which is performedprior to passing the pig through the pipeline, establishing a known timerelationship between the timing means carried by the pipeline pig andthe timing means located externally of the pipeline.
 4. The methodclaimed in claim 2 where the step of externally producing timeindications includes, sensing the passage of the pipeline pig past saidknown locations by the use of externally located sensing means thatproduces respective detection signals, and producing said timeindications in response to said detection signals.
 5. A method forindentifying on a pipeline inspection record the relative position of aknown location along the pipeline, said method comprising the stepsperforming an inspection of the pipeline with apparatus that movesthrough the pipeline and past said known location, making on theapparatus a first record of inspection signals as the apparatus movesthrough the pipeline, simultaneously with the performance of theinspection, providing on said record of inspection signals successivelyoccurring indications of time, detecting the presence of said apparatusat a known location along the pipeline, and external to the pipeline,providing a detection signal upon detection of the apparatus, providingin response to said detection signal, and with means that includes atimepiece located external to the pipeline, a representation of the timethe moving apparatus was detected at said known location, comparing arecord having said inspection signals and said successively occurringtime indications thereon with said representation of the time that theinspection apparatus arrived at said known location to identify the timeindication on the record which corresponds to the time that theapparatus arrived at the known location.
 6. The method claimed in claim5 and further including the steps producing in response to the detectionsignal a coded signal identifying said known location, transmitting thecoded signal to a base station located remotely from the known location,receiving the transmitted coded signal at the base station, producing atthe base station successively occurring time signals that bear a knowntime relationship to the indications of time recorded on the firstrecord, recording on a second record at the base station the time signalproduced there which represents the time the coded signal was receivedfrom the known location, and comparing the first and second records toidentify the time indication on the first record which corresponds tothe time signal on the second record.
 7. A method for making a pipelineinspection record having thereon indications of known external locationsalong the route of the pipeline, said method comprising the stepsplacing one of a plurality of timepieces in a pipeline pig and placingthe remainder of said timepieces external to the pipeline to beinspected, establishing a known time relationship betwEen saidtimepieces, moving the pipeline pig containing said one timepiecethrough the pipeline, performing nondestructive inspection of thepipeline with apparatus carried by the pig as it moves through thepipeline and past said known external locations, making in the pig acontinuous record of nondestructive inspection signals as the pig movesthrough the pipeline, simultaneously with the recording of inspectionsignals, recording on said record successively occurring representationsof time as determined by said one timepiece, sensing externally of thepipeline to detect the arrival of the pig at the respective knownlocations, producing respective indications of time as determined by theexternally located remainder of the timepieces in response to saidsensing of the pig at the known locations, removing said record from thepipeline pig, searching said record of inspection signals andsuccessively occurring time representations, or a record correspondingthereto, to identify the positions on the record where the timerepresentations correspond to said indications of time.
 8. The methodclaimed in claim 7 wherein the step of producing respective indicationsof time in response to said sensing of the pig at the known locationsincludes the steps transmitting a respective signal from each knownlocation in response to the sensing of the pig thereat, receiving saidtransmitted signals at a base station located remotely from said knownlocations, said remainder of the timepieces being located at said basestation, successively recording at the base station respective timeindications provided by said remainder of the timepieces in response tosaid successively received signals.
 9. The method claimed in claim 8 andincluding the steps playing back the record produced in said pig and therecord produced at said base station and producing playback inspectionsignals and respective playback time signals of recorded times on saidrecords, correlating the playback time signals, producing a correlatingsignal when the playback time signals are in correlation, simultaneouslywith the playing back of said two records, producing a third record ofthe playback inspection signals, and producing an indicia on said thirdrecord in response to said correlating signal to indicate adjacent theinspection signals the relative positions of the known locations. 10.Apparatus for making a pipeline inspection record and for indicating onthe record the relative position of a known location along the route ofthe pipeline, comprising the combination inspection apparatus forproviding inspection signals representing detected pipeline conditions,means for moving the inspection apparatus through the pipeline, timingmeans moving with the inspection apparatus through the pipeline forproviding time signals, means included with said inspection apparatusfor simultaneously recording said inspection signals and said timesignals, means external to the pipeline for providing a second timesignal indicating the time the moving apparatus arrived at said knownlocation, playback means for playing back the record of inspectionsignals and time signals and for making an inspection record of saidinspection signals, correlating means operating simultaneously with saidplayback means for correlating playback time signals with a signalcorresponding to said second time signal for producing an indiciumsignal when correlation is achieved, and means for entering an indiciumon said inspection record when correlation is achieved in thecorrelating means.
 11. Apparatus claimed in claim 10 and furtherincluding means for establishing a known time relationship between saidtiming means and the means external to the pipeline, said known timerelationship being established prior to inserting the pipelineinspection apparatus within the pipeline.
 12. Apparatus fOr making apipeline inspection record and for indicating on the record the relativeposition of a known location along the route of the pipeline, comprisingthe combination inspection apparatus for providing inspection signalsrepresenting detected pipeline conditions, means for moving theinspection apparatus through the pipeline, timing means moving with theinspection apparatus through the pipeline for providing time signals,means included with said inspection apparatus for simultaneouslyrecording said inspection signals and said time signals, means includinga second timing means external to the pipeline for providing a record ofthe time the moving apparatus arrived at said known location, saidsecond timing means having a known time relationship to the timing meansmoving with the inspection apparatus, means for comparing said tworecords to identify the time signal on the record made on the inspectionapparatus which corresponds to the recorded time that the device arrivedat said known location.
 13. Apparatus for making a pipeline inspectionrecord and for indicating on the record the relative positions of knownlocations along the route of the pipeline, comprising the combinationinspection apparatus for producing inspection signals representingdetected pipeline conditions, means for moving the inspection apparatusthrough the pipeline and past said known locations, a first timing meansincluded with said apparatus for producing time signals as the apparatusmoves through the pipeline, means included with said apparatus forsimultaneously recording said inspection signals and said time signalsas the apparatus moves through the pipeline, means located externally ofthe pipeline at each of said known locations for detecting the presenceof said apparatus at each of the respective locations and for producingrespective detection signals upon detection of said apparatus at each ofsaid locations, additional timing means located externally of thepipeline, the additional timing means having a predetermined timerelationship with the first timing means, means external to the pipelineand operably connected with said additional timing means for producing arespective time indication in response to each of said detectionsignals, and means for comparing the recorded time signals on the recordmade in the pipeline with the respective time indications producedexternally of the pipeline to identify the time signals which wererecorded when the apparatus was detected at the respective knownlocations.
 14. The apparatus claimed in claim 13 where the additionaltiming means located externally of the pipeline includes a plurality oftimepieces each located at a respective known location, and wherein saidmeans operably connected to the additional timing means includesrespective means at each known location responsive to a respectivedetection signal for causing the respective timepiece to produce a timeindication.
 15. The apparatus claimed in claim 13 wherein the meansexternal to the pipeline and operably connected to said additionaltiming means includes, transmitting means located at each of saidlocations and responsive to a respective detection signal fortransmitting a corresponding detection signal to a base station locatedremotely from the known locations, receiving means located at said basestation for receiving said corresponding detection signals from theknown locations, said additional timing means comprising a second timingmeans at said base station, means responsive to said receivedcorresponding detection signals and operable with said second timingmeans for producing a second record of successive time indicationsproduced by the second timing means at the times that respectivecorresponding detection signals were received.
 16. The apparatus claimedin claim 15 and further including playback means for simultaneouslyplaYing back the record produced in the pipeline and the second recordproduced at the base station, thereby to produce corresponding playbackinspection signals, playback time signals, and playback timeindications, means for correlating said playback time signals and saidplayback time indications to produce a correlation signal each time apredetermined correlation is achieved, means for producing a thirdrecord of playback inspection signals, and means responsive tocorrelation signals for providing an indicium on said third record toidentify the inspection signals that occur in coincidence with acorrelation signal, thereby to locate on said third record the relativepositions of said known locations.
 17. The apparatus claimed in claim 16and further including means responsive to said playback time signals forrecording corresponding times on said third record along with therecorded inspection signals.